1. Field of the Invention
The present invention relates to a sheet feeding device for feeding, supporting, and transporting sheets by means of suction disks.
2. Description of the Related Art
Well known conventional sheet feeding devices used in image forming apparatus and the like generally use suction disks to pick up a single uppermost sheet from a stack containing a plurality of sheets, and transport said sheet to an image forming section. Such sheet feeding devices are advantageous in that they seldom damage the fed sheet, and suppress the generation of paper dust. However, in such sheet feeding devices, there is some paper dust generated from the sheets, as well as dust, dirt, soiling and the like generated in sections other than the sheet feeding device. Such paper dust, dirt and the like adheres to and accumulates on the suction disks of the sheet feeding device, thereby reducing the suction power of the suction disks and eventually rendering them ineffective such that sheets cannot be fed. Accordingly, the suction disks must be cleaned at regular intervals to prevent paper feeding insufficiency.
Generally, the user must be advised beforehand of the necessity of cleaning the suction disks at regular intervals, the user must open the apparatus in accordance with the need for such cleaning and manually clean the suction disks. This cleaning operation is quite a nuisance from the perspective of the user. When the image forming apparatus is a compact printer and the like, or when a photosensitive type sheet is used such that the apparatus must be opened without allowing light to enter into the interior thereof, the apparatus cannot be opened sufficiently so that the cleaning operation is very cramped. Thus, the cleaning operation becomes quite difficult to perform and poses a serious problem.
Alternatively, Japanese Laid-Open Patent Application No. 3-8136 discloses an arrangement whereby a sheet coated by a sticky cleaning material is suctioned by the suction disks so as to be picked up thereby and clean said suction disks, and thus render the manual cleaning operation by an operator unnecessary. However, when material having a high degree of stickiness is used for the cleaning material, the suctioned sheet coated by the sticky material is difficult to separate from the suction disks, which leads to the fear of paper feeding insufficiency. On the other hand, when material having a low degree of stickiness is used for the cleaning material, the suction disks are not adequately cleaned. Furthermore, in such apparatus, when a sheet coated by a cleaning material is loaded in the paper accommodating portion such that the sheet coated by the cleaning material comes into contact with a sheet used for printing, the sheet used for printing may undergo a change of properties and may be damaged so as to cause sheet feeding insufficiency.